This invention relates to compact fluorescent lamp units and, in particular, to a compact fluorescent lamp unit for a three-way incandescent-type lamp fixture.
It is well known that a fluorescent lamp is more efficient than a incandescent lamp by a factor of three to four or more for equivalent illumination and that a fluorescent lamp has a much longer service life compared to that of a incandescent lamp. In the past, fluorescent lamps have not been used to any appreciable degree for indoor residential lighting because of their poor color rendering properties, as compared to incandescent lighting. In recent years, though, fluorescent lamps are available with both a high luminous output and a color appearance and color rendition comparable to incandescent. Increased residential use of fluorescent illumination, with attendant savings of energy can be achieved from the development of fluorescent lamp systems which are directly compatible with existing incandescent-type sockets.
One such lamp system is disclosed in U.S. Pat. No. 2,817,004 dated Dec. 17, 1957, issued to Baumgartner, et al. This patent discloses a combined adapter and holder for circular tubular fluorescent lamps. The combined adapter and holder are mountable on existing light fixtures designed for incandescent lamps equipped with screw-type bases and with the plane of the circular lamp envelope being essentially vertical.
In an article appearing in Lighting Design and Application, Mar. 1976 edition, entitled "Conversion of Incandescent Lamp Sockets to Fluorescent in the Home Market" by E. A. Dale, a retrofit lighting system for converting incandescent fixtures to fluorescent is disclosed.
In U.S. Pat. No. 4,178,535, dated Dec. 11, 1979, issued to Jack V. Miller is disclosed a three-way brightness fluorescent lampholder fitting, utilizing one or more ballast inductors.